1. Field of the Invention
The present invention relates to a positive-tone radiation-sensitive composition and a resist pattern-forming method.
2. Discussion of the Background
In the field of microfabrication such as production of integrated circuit devices, lithographic technology that enables microfabrication with a line width of 0.10 μm or less has been desired to achieve a higher degree of integration.
Lithographic technology that can form a finer pattern (e.g., a fine resist pattern with a line width of about 45 nm) is expected to be required. Such a fine pattern may be formed by reducing the wavelength of the light source of the exposure system (e.g., ArF excimer laser (wavelength: 193 nm)), or increasing the numerical aperture (NA) of the lens, for example. However, an expensive exposure system is required to reduce the wavelength of the light source. When increasing the numerical aperture (NA) of the lens, since the resolution and the depth of focus have a trade-off relationship, a decrease in depth of focus occurs when increasing the resolution.
In recent years, liquid immersion lithography has been proposed as lithographic technology that can solve the above problems.
However, it is considered that liquid immersion lithography can only be applied up to 45 nm half pitch (hp). Therefore, technical development toward a 32 nm hp generation has been conducted. In recent years, technology that forms a 32 nm line-and-space (LS) pattern by forming isolated line patterns or trench patterns by a half pitch utilizing double patterning (DP) or double exposure (DE) has been proposed to deal with a demand for an increase in complexity and density of devices (see SPIE 2006 61531K, for example).
Specifically, when forming a 32 nm LS pattern, 32 nm lines are formed at a pitch of 1:3. A hard mask (hereinafter may be referred to as “HM”) (e.g., SiO2) is formed by etching, and 32 nm lines are formed at a pitch of 1:3 at positions displaced from the first-layer resist pattern by a half pitch. A hard mask (HM) is then formed by etching to obtain 32 nm lines at a 1:1 pitch.
However, a material that may suitably be used for double exposure utilizing liquid immersion lithography has not been proposed. Moreover, when forming a second-layer resist pattern using the above method after forming a first-layer resist pattern, the first-layer resist pattern may be deformed, so that the lines may be formed with insufficient accuracy.